1. Field of the Invention
The present invention relates to a rotary ring for spinning. More particularly, the present invention relates to a rotary ring including a ring-shaped rotary member rotated by a torque caused by a sliding friction given thereto by a traveller running thereon, and equipped with an improved braking mechanism thereof.
2. Description of the Related Art
A rotary ring comprising a holder, a bearing, and a ring-shaped rotary member supported rotatably through the bearing by the holder and rotated by a torque caused by a sliding friction given thereto by a traveller rotating thereon is known from, for example, Japanese Unexamined Patent Publication (Kokoku) No. 54-15934. Generally, the above type rotary ring is called a negative rotary ring for spinning, because this rotary ring is not equipped with a positive means of driving the ring-shaped rotary member.
In the negative rotary ring, it is necessary to provide a means for preventing an overrun of the ring-shaped rotary member generated when a spinning frame with the negative rotary rings is stopped. As the overrun preventing mechanism of the negative rotary ring, a rotation controlling mechanism is provided for controlling a rotation of the ring-shaped rotary member by a resistance of a wing or a protrusion attached thereto in a fluid such as an air or a liquid, or a braking mechanism for preventing an inertial rotation of the ring-shaped rotary member by mechanically applying a grasping force to the ring-shaped rotary member by using, for example, a lever or the like, are known.
The known ring-shaped rotary member overrun preventing mechanism has several disadvantages. For example, the mechanism having a wing capable of applying a resistance in air has a disadvantage in that, when a spindle and the corresponding ring-shaped rotary member are rotated at a high speed, and thus the inertial rotation becomes large, it is impossible to prevent an overrun of the ring-shaped rotary member. Although the mechanism disclosed in Japanese Unexamined Patent Publication No. 62-263331, in which a ring-shaped rotary member having a wing or a protrusion on a lower side thereof is used, can prevent the overrun of the ring-shaped rotary member by raising an oil bath when a spinning frame is stopped, to apply a braking force due to a resistance of the oil to the ring-shaped rotary member, this mechanism can apply only a simultaneous braking force on all of the ring-shaped rotary members in the spinning frame, and cannot apply the braking force for each ring-like rotary member individually. The mechanism disclosed in Japanese Unexamined Patent Publication No. 62-206036, in which a ring shaped rotary member having a lower end protruded from an under side of a ring rail is used, can prevent the overrun of the ring-shaped rotary member by directly applying a grasping force through a lever or the like to the ring-like rotary member, but has the same disadvantage as that of the mechanism disclosed in the Japanese Unexamined Patent Publication No. 62-26331. Namely this mechanism cannot be used to individually brake each ring-like rotary member.
When the ring-shaped rotary ring is synchronously rotated at a maximum rotational speed of a traveller the ring-shaped rotary member overruns in a movement of a thread in each chase of a cop. When the overrun of the ring-shaped rotary member is generated, a ballooning tension of a thread between a snarl wire and a traveller changes remarkably irregularly, resulting in breakage of the thread in spinning. Further, it must be noted that the irregularity of the ballooning tension of the thread differs for each spindle. Therefore when the rotation of the spindle increases to a high value, e.g., 20,000 r.p.m. or 25,000 r.p.m., it becomes to necessary to individually control the rotation of each ring-shaped rotary member, to obtain a thread having a superior quality under a staple spinning condition.
From the above-described viewpoint, the same applicant as that of the present application proposed a braking mechanism comprising a ring-shaped rotary member having a braking shoe capable of bending toward a lower end of a holder supporting, through a bearing, the ring-shaped rotary member, in Japanese Examined Patent Publication No. 63-42009 published on Aug. 19, 1988. The braking shoe can be brought into contact with the lower end of the holder when a rotation of the ring-shaped rotary member exceeds the predetermined value, and accordingly, it is possible to individually control the rotation of each ring-shaped rotary member in the spinning frame. Since the rotational speed at which the braking shoe comes into contact with the holder can be optionally selected according to a material of the braking shoe, and selecting the width of a gap between the lower end face of the holder and an upper face of the braking shoe or the like, it is possible to determine a maximum rotational speed of the ring-shaped rotary member by suitably selecting the above conditions. Nevertheless, this braking mechanism has still another disadvantage in that a difference between a rotational speed of the spindle and the rotational speed of the ring-shaped rotary member depends on the rotational speed of the spindle. For example, even if the difference between the rotational speed of the spindle and the rotational speed of the ring-shaped rotary member is kept constant by suitably selecting the conditions of the braking shoe, when the spinning frame is stopped, the spindle can be stopped in a relatively short time, but the rotation of the ring-shaped rotary member is continued for a relatively long time due to a rotational inertia of the ring-shaped rotary member, and this results in an overrun of the ring-shaped rotary member and a generation of a snarl in the thread. Accordingly, it is possible to provide a braking mechanism enabling a rotation of the spindle at up to 20,000 r.p.m., and to keep the rotational speed of the ring-shaped rotary member constant, e.g., at 12,000 r.p.m., with the above-mentioned, braking mechanism, but to avoid the generation of an overrun of the ring-shaped rotary member when the spinning frames are stopped, the rotational speed of the ring-shaped rotary member must be allowed to fall to about 5,000 r.p.m. to 6,000 r.p.m.
To eliminate this disadvantage of the braking mechanism disclosed in Japanese Examined Patent Publication No. 63-42009, the same applicant as that of the present application further proposed an improved braking mechanism in which a contact area between the lower end face of the holder and the upper face of the braking shoe can be adjusted according to a value of the rotational speed of the ring-shaped rotary member, in Japanese Patent Application No. 1-122024 filed on May 15, 1989.
This improved braking mechanism will be explained in detail with reference to FIGS. 7 and 8.
FIG. 7 shows an axial cross sectional view of an example of the improved braking mechanism, and FIG. 8 shows another cross sectional view of another example thereof.
A braking shoe 125 shown in FIG. 7 is comprised of a vertical portion 51, a bending portion 53, and an inclining portion 52; an upper face of the inclining portion 52 being a flat plane. A lower end face 48 of a holder 11 shown in FIG. 7 is a curved face. Conversely, in a braking shoe 126 shown in FIG. 8, an upper face of an inclining portion 54 is a curved face, and a lower end face 49 of a holder 11 shown in FIG. 8 is a flat plane.
When a ring-shaped rotary member 13 is rotated and a rotational speed of the ring-shaped rotary member 13 is increased, a centrifugal force applied to the inclining portion 52 or 54 is increased, and thus the inclining portion 52 or 54 is turned about the bending portion 53 from the position 125 illustrated by a solid line to the position 125' illustrated by a two-dot-chain line in FIG. 7, and from the position 126 illustrated by a solid line to the position 126a illustrated by a two-dot-chain line or the position 126b illustrated by another two-dot-chain line.
The inclining portion, i.e., the portion 52 or 54, is made of a resilient material, and accordingly, a bending angle of the inclining portion about the bending portion can be changed according to the centrifugal force, i.e., the rotational speed of the ring-shaped rotary member, and thus a contacting area between the upper face of the inclining portion 52 or 54 and the lower end face of the holder is changed according to the rotational speed of the ring-shaped rotary member, resulting in an increase of a braking force therebetween. This phenomenon is clearly illustrated in FIG. 8 and the inclining portion having a posture shown by the inclining portion 126a when the rotational speed of the ring-shaped rotary member is relatively lower is changed to a posture shown by the inclining portion 126b when the inclining speed of the ring-shaped rotary member becomes high. Consequentially, this improved braking mechanism can brake the rotation of the ring-shaped rotary member over a broad speed range compared with the conventional rotary ring described herebefore, and prevent the generation of an overrun of the ring-shaped rotary member when the spinning frame is stopped and the rotation of the ring-shaped rotary member is continued due to an inertia thereof.
Nevertheless, this improved braking mechanism has another disadvantage. Namely, since a time for which the inclining portion is contact with the holder and a continuous friction therebetween is also long, in this braking mechanism, the inclining portion is likely to be abraded when using this braking means for a long period, e.g., several years. Further this improved braking mechanism can brake the ring-shaped rotary member so that the rotational speed thereof is suitably controlled over a broad speed range, as described above, but it is impossible to absorb an irregularity of the thread tension of the thread during spinning by this improved braking mechanism, after the inclining portion is completely in contact with the holder. The reason for this phenomenon appears to be that, since a resilient material is used as the inclining portion of the braking shoe; the friction in the rotational direction of the ring-shaped rotary member between the holder and the ring-shaped rotary member is large, and a braking force cannot precisely compensate for the rotational speed of the ring-shaped rotary member.